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Welcome! If you’re looking to learn SQL (Structured Query Language), you’re in the right place. This tutorial delivers an easily digestible and newbie-friendly introduction to the world of databases.
What is SQL?
SQL is a language used for interacting with databases. It allows you to access, manipulate, and carry out instructions on database structures and data. Regardless of the size of your data set, if it is a database, most likely SQL is behind the scenes, making things rock and roll.
Getting Started: SELECT statement
One of the most fundamental aspects of SQL is the SELECT statement, used to select data from a database. The data returned is stored in a result table also called the result-set.
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SELECT column1, column2, ... FROM table_name; |
Example:
For instance, consider a database for a bookstore with a table named ‘Books’. If we want to select the titles of all the books in ‘Books’ table, we would use the following code:
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SELECT title FROM Books; |
The WHERE Clause
The WHERE clause is used to filter records – it extracts only those records that fulfill a specified condition.
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SELECT column1, column2, ... FROM table_name WHERE condition; |
Example:
If we want to select books from the ‘Books’ table that have ‘Science’ as their category, we could use a WHERE clause as follows:
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SELECT title FROM Books WHERE category = 'Science'; |
JOIN Operations
The SQL JOIN clause combines rows from two or more tables, based on a related column between them. It’s a powerful tool when understanding relationships between different data points.
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SELECT Orders.OrderID, Customers.CustomerName FROM Orders JOIN Customers ON Orders.CustomerID = Customers.CustomerID; |
Example:
Lets say we have another table, ‘Authors’, and we want to pull a list of books and their authors, we can use a JOIN operation:
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SELECT Books.title, Authors.name FROM Books JOIN Authors ON Books.author_id = Authors.author_id; |
We will delve into more complex operations in future posts, but for now, it’s crucial to have a grip on these fundamentals. The door to data analysis and management is open, and SQL is the key!
Happy learning!